Catheter ultrasound ablation

ABSTRACT

Apparatus and methods are described including positioning an ultrasound transducer at a blood vessel ostium, rotating the transducer about its axis and scanning tissue of the blood vessel ostium, recording one or more baseline returned signals from the tissue, and creating a baseline image of the blood vessel ostium based on at least one of the returned signals. Tissue of the blood vessel ostium is ablated in consecutive segments by rotating the transducer segmentally until full rotation is completed. The returned signals of the ablated segments are recorded in real-time and a real-time image is created based on the one or more returned signals. Ablation is terminated after changes in the real-time returned signals and/or real-time image with respect to the baseline returned signals and/or baseline image indicate an achieved predetermined level of ablation lesion formation. Other applications are also described.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/260,458 to Sela, filed 14 Jan. 2021, which is the US national phaseapplication of PCT Application No. PCT/IL2019/050941 to Sela (publishedas WO 2020/039442), filed Aug. 22, 2019, which claims the benefit ofpriority to U.S. Provisional Patent Application No. 62/720,995, filedAug. 22, 2018, entitled “CATHETER ULTRASOUND TRANSDUCER CONTAINER”. Thecontents of the above-referenced U.S. Provisional Patent Application isall incorporated by reference as if fully set forth herein in itsentirety.

FIELD OF THE INVENTION

The invention, in some embodiments thereof, relates to catheterultrasound (US) transducers.

BACKGROUND

Catheter ablation is a procedure used to remove or terminate a faultyelectrical pathway from sections of the heart, especially in those whoare prone to developing cardiac arrhythmias and to restore the heart toits normal rhythm. Ablation procedures are commonly carried out byradiofrequency (RF) ablation and cryoablation.

Catheter ablation is a specialist catheter-based procedure that ablatesabnormal heart muscle tissue. The procedure is used particularly inpatients whose cardiac arrhythmia cannot be controlled with medication.

Catheter ablation involves advancing several flexible catheters into thepatient's blood vessels, usually either in the femoral vein, internaljugular vein, or subclavian vein. The catheters are then advancedtowards the heart. Electrical impulses are then used to induce thearrhythmia and local heating or freezing is used to ablate the abnormaltissue that is causing it. Catheter ablation is usually performed by anelectrophysiologist (a specially trained cardiologist) in a catheter labor a specialized EP lab.

The foregoing examples of the related art and limitations relatedtherewith are intended to be illustrative and not exclusive. Otherlimitations of the related art will become apparent to those of skill inthe art upon a reading of the specification and a study of the figures.

SUMMARY

There is provided, in accordance with some embodiments of the inventiona catheter US transducer container, including a housing, one or morecooling channels, oriented longitudinally along a longitudinal axis ofthe container, a sealing cooling channel cover, one or more PE elementspositioned on a floor of the cooling channel and having an emittingsurface facing the cover, wherein the cooling channel has a trapezoidcross section at any point along the PE element.

In some embodiments, an emitting surface of at least one PE element isoriented in parallel to the cooling channel cover. In some embodiments,the floor includes the short base of the trapezoid. In some embodiments,the housing further includes at least one fluid inlet opening to aproximal end of the cooling channel and at least one fluid outletlocated at a distal end of the cooling channel and/or located inside thefluid collecting and diverting chamber and a fluid collecting anddiverting chamber coupled to a distal end of the cooling channel.

In some embodiments, the housing includes at least one post coupled tothe floor of the cooling channel and supports the PE element, forming agap between the floor and the PE element. In some embodiments, the PEelement is angled with respect to the floor of the cooling channel. Insome embodiments, the cooling channel cover and the emitting surface ofthe PE element are parallel. In some embodiments, the cooling channel isconfigured to promote laminar flow of fluid flowing between the coverand the emitting surface of the PE element.

In some embodiments, the rate of flow of the fluid flowing the coolingchannel is adjusted to the viscosity of the fluid and fluid velocitywithin the cooling channel is maintained below a threshold at which itbecomes turbulent. In some embodiments, in operation, the laminar flowpromoted by the geometry and dimensions of the fluid channel. In someembodiments, the laminar flow effected by the geometry and design of thecooling channel forms a temperature gradient in the fluid in the coolingchannel along a distance (L) between the emitting surface of the PEelement and the fluid channel cover and the temperature gradientmaintains a temperature at the cooling fluid channel cover at or belowtemperature of blood surrounding the container.

In some embodiments, the container includes a plurality of PE elementsangled with respect to one another. In some embodiments, the containerincludes a plurality of PE elements at least one of which is angled withrespect to the cooling channel floor. In some embodiments, at least oneof the PE elements is an ablative PE element and at least one of the PEelements is an imaging PE element. In some embodiments, a depth (d) ofthe cross-section of the cooling channel is smaller than the radius ofthe housing. In some embodiments, a diameter of the container isunchangeable. In some embodiments, the housing includes at least onetemperature sensor.

In some embodiments, the PE element includes a first and a secondelectrodes, the first electrode disposed along the emitting surface anda second electrode disposed along an opposite surface of PE element,wherein the PE element includes a first and a second electrodes, thefirst electrode is disposed along at least a portion of the PE elementemitting surface and around one end of the PE element and a secondelectrode disposed along at least a portion of an opposite surface of PEelement and around an opposite end of the PE element.

In some embodiments, the electrodes are isolated from each other by atleast one gap on the emitting surface and the opposite surface of the PEelement, wherein the at least one gap is bridged by an insulatingadhesive.

In some embodiments, the catheter includes at least one positioner. Insome embodiments, the positioner is in a form of a basket. In someembodiments, the positioner is in a form of a coil. In some embodiments,the positioner is in a form of an umbrella. In some embodiments, thepositioner may comprise an opening facing towards the US transducercontainer. In some embodiments, the positioner may comprise an openingfacing away from the US transducer container. In some embodiments, thepositioner includes at least one opening.

In some embodiments, the positioner is non-occluding. In someembodiments, the positioner is disposed over the container. In someembodiments, the container is disposed between two positioners.

In some embodiments, the container is rotatable about the catheter. Insome embodiments, the container includes a beam collimating acousticlens. In some embodiments, the beam collimating acoustic lens isconfigured to collimate an US beam and generate a jet effect insurrounding blood along the beam pathway through the blood. In someembodiments, the collimating acoustic lens is configured to direct thejet effect towards and cool the ablated tissue.

In some embodiments, the catheter includes a medicament outlet inpropinquity to the container and wherein the collimating acoustic lensis configured to direct the jet effect towards and drive the medicamentinto tissue.

In some embodiments, the processor is configured to adjust the level ofenergy emitted from the PE element based on at least one of distancemeasured from the emitting surface of the PE element to the tissue wall,tissue thickness, duration of energy delivery, change in amplitudeand/or phase of ultrasound signal returning from the tissue andreduction of recorded electrical potential signals. In some embodiments,the processor is configured to adjust fluid flow velocity in the coolingchannel based on the temperature reading and beam energy level. In someembodiments, the cooling fluid channel includes a fluid inlet and theprocessor is configured to adjust fluid temperature at the inlet basedon the temperature reading and beam energy level.

In some embodiments there is provided a method of manufacture of acatheter US transducer container, including molding a housing having atleast one cooling fluid channel, at least one PE element mounting post,and at least one wiring conduit, laying electrical and data wiringinside the wiring conduits, mounting at least one PE element on the atleast one mounting post and within designated cavities in coolingchannel and connecting wiring, sealing a perimeter of the PE element towalls of the cooling channel attaching a cooling fluid collecting anddiverting chamber to a distal end of the housing, and placing aninsulating cover over the housing and cooling channel, shrinking thecover and tightly sealing the housing and the cooling channel.

The following embodiments and aspects thereof are described andillustrated in conjunction with systems, tools and methods which aremeant to be exemplary and illustrative, not limiting in scope.

In addition to the exemplary aspects and embodiments described above,further aspects and embodiments will become apparent by reference to thefigures and by study of the following detailed description.

BRIEF DESCRIPTION OF THE FIGURES

Exemplary embodiments are illustrated in referenced figures. Dimensionsof components and features shown in the figures are generally chosen forconvenience and clarity of presentation and are not necessarily shown toscale. The figures are listed below.

FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, II, 1J and 1K are perspective viewand cross section view simplified illustrations of an US transducercontainer, according to some embodiments of the invention;

FIGS. 2A, 2B and 2C are cross section view simplified illustrations ofthe US transducer container cooling system, in accordance with someembodiments of the current invention;

FIG. 3A is a perspective view simplified illustration of US transducercontainer cooling system, and FIGS. 3B and 3C are a graph and heatdistribution map demonstrating heat distribution within the coolingsystem, in accordance with some embodiments of the invention;

FIGS. 4A and 4B are longitudinal cross-section view and transverse crosssection view simplified illustrations of the effect of laminar coolingfluid flow on bubbles, in accordance with some embodiments of thecurrent invention;

FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H and SI, are perspective view andcross section view simplified illustrations of method of manufacturing acontainer transducer, in accordance with some embodiments of theinvention;

FIG. 6 is a flow chart of a method of manufacture and assembly of an UStransducer container, in accordance with some embodiments of theinvention;

FIGS. 7A, 7B, 7C, 7D, 7E, 7F, 7G and 7H are plan view and perspectiveview simplified illustrations of a positioner for an US transducercontainer, in accordance with some embodiments of the invention; and

FIG. 8 is a cross section view simplified illustration of a jet effectgenerated by an US transducer container, in accordance with someembodiments of the invention;

FIG. 9 is a transverse cross-section simplified illustration of amultidirectional US transducer container, according to some embodimentsof the invention; and

FIGS. 10A and 10B are perspective view simplified illustrations of acombination US transducer/RF electrode catheter container, according tosome embodiments of the invention.

DETAILED DESCRIPTION

According to an aspect of some embodiments of the invention there isprovided a catheter US transducer having one or more PiezoElectric (PE)elements (ceramics) and one or more cooling systems that regulate thetemperature of the transducer and/or volumes adjacent to the UStransducer (e.g., cooling fluid). According to some embodiments, the UStransducer and the cooling system are housed within a container. In someembodiments, the container comprises one or more apertures.

In some embodiments, the cooling systems comprises cooling fluid. Insome embodiments, the cooling system is circulated within the container.In some embodiments, the container is sealed from the environment. Insome embodiments, the cooling fluid does not contact fluid surroundingthe catheter and/or the container. In some embodiments, the externaldiameter of the container is smaller than the external diameter of thecatheter. In some embodiments, the external diameter of the container isthe same as the external diameter of the catheter. In some embodiments,the external diameter of the container is larger than the externaldiameter of the catheter. In some embodiments, the temperature of theexternal surface of the US transducer container is maintained below 45°C. In some embodiments, the container is rigid. In some embodiments, theexternal diameter of the US transducer container is unchanged duringoperation.

According to an aspect of some embodiments of the invention there isprovided an US transducer container sized and fitted to be positionedalong a catheter and/or within a delivery catheter. In some embodiments,the US transducer emitting surface comprises a plane one dimension ofwhich is oriented in parallel to a longitudinal axis of the catheter. Insome embodiments, the US transducer emitting surface comprises a planeone dimension of which is angled with respect to the longitudinal axisof the catheter. In some embodiments, the US transducer comprises aplurality of emitting surfaces, in which at least one emitting surfacecomprises a plane one dimension of which is oriented in parallel to alongitudinal axis of the catheter and at least a second emitting surfacecomprises a plane having at least one dimension that is angled withrespect to the longitudinal axis of the catheter. In some embodiments,the US transducer comprises a plurality of emitting surfaces, in whichat least two emitting surfaces are angled with respect to thelongitudinal axis of the catheter. In some embodiments, the at least twoemitting surfaces are inclined towards each other with respect to thelongitudinal axis of the catheter.

According to an aspect of some embodiments of the invention there isprovided an US transducer container sized and fitted to be positionedalong a catheter and/or within a delivery catheter. In some embodiments,the US transducer container comprises a collimating acoustic lens. Insome embodiments, the US transducer emits a collimated beam. In someembodiments, the collimated beam generates one or more jets in the bloodstream (a jet effect). In some embodiments, a collimated beam generatesthe jet effect in surrounding blood along the beam pathway through theblood. In some embodiments, the generated jets are at the sametemperature as the medium in which they are generated.

According to an aspect of some embodiments of the invention there isprovided one or more US transducer positioners. In some embodiments, thepositioner is in a form of a basket. In some embodiments, the positioneris in a form of a cage. In some embodiments, the positioner is in a formof a coil. In some embodiments, the transducer catheter comprises twopositioners disposed one on either side of the US transducer container.In some embodiments, the positioner is made of a shape memory alloy. Insome embodiments, the positioner envelops the US transducer container.In some embodiments, the positioner comprises an aperture. In someembodiments, the diameter of the aperture is greater than the diameterof the US beam emitted through the aperture.

According to some embodiments of the invention, the catheter comprisesone or more therapeutic agent delivery nozzles configured to deliver atherapeutic agent into a volume within an emitted US beam. In someembodiments, the US transducer emits collimated beam energy. In someembodiments, the collimated beam energy generates one or more jets inthe blood stream (a jet effect) that drive the therapeutic agent via thejet stream towards the tissue surface.

General

Reference is now made to FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, II, 1Jand 1K, which are perspective view and cross section view simplifiedillustrations of a catheter US transducer container according to someembodiments of the invention. According to some embodiments of theinvention there is provided a catheter US transducer 175 housed incontainer 100. In some embodiments, container 100 comprises one or morecooling systems 200 that regulate the temperature of the transducer 175by streaming cooling fluid over and around the US transducer. Accordingto some embodiments, the US transducer 175 and the cooling system 200are housed within the container 100. In some embodiments, the container100 comprises one or more apertures 118. In some embodiments, one ormore of the apertures 118 comprise one or more blood-contact surfaces116.

In some embodiments, the container 100 is fluidly sealed from theenvironment. In some embodiments, the cooling fluid does not contactfluid surrounding the catheter and/or the container 100. In someembodiments, the external diameter of the container 100 is smaller thanthe external diameter of the catheter 106. In some embodiments, theexternal diameter of the container 100 is the same as the externaldiameter of the catheter. In some embodiments, the external diameter ofthe container is larger than the external diameter of the catheter 106.In some embodiments, the temperature of the external surface of the UStransducer container 100 is maintained below 45° C.

In some embodiments, US transducer container 100 is attached to acatheter 106 end and functionally coupled to one or more sources ofcooling fluid, power (e.g., electric power), vacuum and unidirectionaland/or bidirectional data communication conduits. Catheter 106 comprisesa main lumen 126. The term “Cooling Fluid” as used herein relates to afluid having a temperature configured to maintain a temperature of ablood-contact surface 116 no higher than the surrounding bloodtemperature.

In some embodiments, the US transducer 175 container 100 is mounted at adistal end of a catheter 106. In some embodiments, the US transducercontainer 100 is mounted proximally to the catheter tip. In someembodiments, the external diameter of the US transducer container 100 isunchanged before, during and/or post operation.

As used herein the term “Proximal” means closer to the user of the UScatheter and the term “Distal” means closer to the tip of the UScatheter. The term “proximally” means towards the user of the UScatheter and the term “Distally” means away from the user of the UScatheter and towards the tip of the US catheter.

In some embodiments, and as shown in the exemplary embodiments depictedin FIGS. 1A and 1B, catheter ultrasound transducer container 100 has acylindrical geometry and comprises a housing 502. In some embodiments,at least one or more portions of housing 502 are solid. In someembodiments, housing 502 comprises one or more hollow conduits thatprovide passageways for example, for electrical and/or datacommunication wiring, a coolant, medicament and/or any other fluid froma source to the US transducer container 100. In some embodiments, asolid portion of housing 502 fills over 50% of the cross-section ofhousing 502. In some embodiments, the solid portion of housing 502 fillsbetween 50% and 75% of the cross-section of housing 502.

In some embodiments, housing 502 comprises one or more trough-formcooling channels 120, disposed longitudinally along a longitudinal axisof container 100 and catheter 106 and configured to promote laminarfluid flow. In some embodiments, cooling channel 120 comprises atrapezoid cross-section (FIG. 2A) defined by a floor 108 and walls122/124, on lateral sides of floor 108 forming an obtuse angle betweenfloor 108 and walls 122/124. In some embodiments, walls 122/124 arepositioned parallel to the longitudinal axis of container 100 andcatheter 106. In some embodiments, the trapezoid is an isoscelestrapezoid. In some embodiments, floor 108 comprises the short base ofthe trapezoid.

In some embodiments, housing 502 comprises one or more posts 102 thatprotrude from floor 108 and support one or more piezoelectric (PE)elements 140 Forming a gap between PE element 140 and floor 108. Thelength of cooling channel 120 is at least the same as the length of PEelement 140. In some embodiments, cooling channel 120 has a trapezoidcross section at any point along at least one or more PE elements 140.

In some embodiments, catheter ultrasound transducer container 100cooling channel 120 comprises one or more cooling fluid inlets 152disposed at a proximal and of cooling channel 120. Cooling channel 120opens distally to a fluid (e.g., coolant) cooling fluid divertingchamber 156. In some embodiments, housing 502 comprises a cooling fluidoutlet 154 disposed at a distal end of cooling channel 120 and/or insidea fluid cooling fluid diverting chamber 156. In some embodiments, fluidcooling fluid diverting chamber 156 is configured to collect fluidflowing through cooling channel 120 over an emitting surface 142 of PEelement 140 and exiting from the distal end thereof, and divert thefluid to drain into fluid outlet 154 and catheter 106 to a fluidcollection reservoir.

In some embodiments, catheter US transducer container 100 is fluidlysealed and isolated from the surroundings e.g., blood. In someembodiments, catheter US transducer container 100 comprises a sealingcooling channel cover 130. In some embodiments, and as explained ingreater detail herein, cover 130 comprises at least two surfaces: a PEelement 140-facing surface and a blood contact surface 116 facing awayfrom PE element 140. In some embodiments, fluid (e.g., coolant) inlet152 disposed between cover 130 and the emitting surface 142 of PEelement 140. In some embodiments, cover 130 is parallel to emittingsurface 142 of PE element 140. In some embodiments, fluid flowing frominlet 152 through cooling channel 120 and between two flat surfaces ofPE element 140 and cover 130 flows at a laminar flow. The rate of flowof the coolant fluid is adjusted to the viscosity of the fluid and fluidvelocity is maintained below a threshold at which it becomes turbulent.

In some embodiments, and optionally, cooling channel 120 comprises oneor more cooling fluid side inlets 128 in walls 122/124 and fluid flowingfrom side inlets 128 through cooling channel 120 and between two flatsurfaces of PE element 140 and cover 130 flows at a laminar flow.

In some embodiments, cooling channel 120 cover 130 completes thetrapezoid cross-section. In some embodiments, cover 130 is flat. In someembodiments, cover 130 is curved. In some embodiments, the depth (d)(FIGS. 2A and 2C) of the cross-section of cooling channel 120 is smallerthan the radius of housing 502. In some embodiments, the depth (d) ofthe cross-section of cooling channel 120 is less than two thirds of theradius of housing 502. In some embodiments, the depth (d) of thecross-section of cooling channel 120 is between two thirds and half ofthe radius of housing 502.

In some embodiments, cover 130 spans less than 50% of the circumferenceof housing 502. In some embodiments, cover 130 spans between 40% and 50%of the circumference of housing 502. In some embodiments, cover 130spans between 30% and 40% of the circumference of housing 502. In someembodiments, cover 130 spans between 20% and 30% of the circumference ofhousing 502. In some embodiments, cover 130 spans less than 20% of thecircumference of housing 502.

PE element 140 emitting surface 142 is positioned parallel to a floor108 of cooling channel 120 and to container 100 longitudinal axis andemits US energy radially outwards in a direction generally perpendicularto the emitting surface 142 of PE element 140. In some embodiments, PEelement 140 is mounted on posts 102 defining a gap 104 between PEelement 140 and floor 108 of cooling channel 120. In some embodiments,gap 104 comprises air that forms a buffer that blocks ultrasonic energyfrom being emitted in the direction of channel floor 108 and increasesthe energy emitted radially outward.

In some embodiments, and as shown in FIG. 1C, PE element 140 is inclinedsloping generally forwards (distally) towards the catheter tip 158 withrespect to floor 108 of cooling channel 120 and to container 100longitudinal axis and is configured to emit US energy generally angledforward (distally) with respect to floor 108 of cooling channel 120 andcontainer 100 longitudinal axis. In some embodiments, and as depicted inFIG. 1D an angle of inclination (a) between 1 and 80 degrees. In someembodiments, the angle of inclination (a) is between 20 and 70 degrees,between 30 and 60 degrees or between 40 and 50 degrees.

In some embodiments, and as depicted in FIG. 1E, PE element 140 isinclined sloping generally proximally (away from catheter tip 158) withrespect to floor 108 of cooling channel 120 and to container 100longitudinal axis and is configured to emit US energy generally angledbackwards (proximally) with respect to floor 108 of cooling channel 120and container 100 longitudinal axis at an angle of inclination (b)between 1 and 80 degrees. In some embodiments, the angle of inclination(b) is between 20 and 70 degrees, between 30 and 60 degrees or between40 and 50 degrees.

A potential advantage of this configuration is in that US energy can beemitted generally perpendicularly towards inclined or sloppy anatomicaltissue e.g., openings or ostia 112 of narrowing blood vessels 110 wallfor ablation purposes. As demonstrated in FIG. 1F, tip 158 of catheter106 is limited from further introduction by a wall 114 of blood vessel110 and in some cases treatment of tissue in the ostium 112 of a bloodvessel 110 can be difficult to impossible.

In some embodiments, and as shown in FIG. 1F, US transducer container100 comprises one or more PE elements 140-1 inclined sloping generallyforwards (distally) towards the catheter tip 158 and one or more PEelements 140-2 parallel to floor 108 of cooling channel 120 andcontainer 100 longitudinal axis. A potential advantage of thisconfiguration is in that US energy can be emitted generally forwardtowards areas having limited access, e.g., ostium 112 of narrowing bloodvessel 110, for ablation purposes. In this configuration ablation USenergy is emitted from PE element 140-1 from a safe distance but maystill be imaged by PE element 140-2 without harm to the treated tissue.

In some embodiments, and as shown in FIG. 1G, US transducer container100 comprises one or more PE elements 140-1 inclined sloping generallyforwards (distally) towards the catheter tip 158 and one or more PEelements 140-2 inclined sloping generally backwards (proximally) awayfrom the catheter tip 158. A potential advantage of this configurationis in that ablation energy can be emitted by one of PE elements 140(e.g., PE element 140-1) and the progress of the ablative procedureimaged by the second PE element (e.g., PE element 140-2). In thisconfiguration ablation US energy is emitted from PE element 140-1 from asafe distance but may still be imaged by PE element 140-2 without harmto the treated tissue.

In some embodiments, and as shown in FIG. 1H, US transducer container100 comprises one or more PE elements 140-1 inclined sloping generallyforwards (distally) towards the catheter tip 158, one or more PEelements 140-2 parallel to floor 108 of cooling channel 120 andcontainer 100 longitudinal axis and one or more PE elements 140-3inclined sloping generally proximally (away from catheter tip 158). Apotential advantage of this configuration is in that US energy can beemitted generally forward and perpendicularly towards areas havingangled or steeped anatomy (e.g., ostia 112 of narrowing blood vessels110) for ablation purposes, or generally backward towards areas havingangled or steeped anatomy (e.g., ostia 112 of narrowing blood vessels110) for ablation purposes. In this configuration ablation US energy isemitted from PE elements 140-1 and/or 140-3 from a safe distance but maystill be imaged by PE element 140-2 without harm to the treated tissue.

In some embodiments, two ablating PE elements 140 (e.g., FIG. 1J, 140-1and 140-2) are set in container 100 spaced from one another by a gape.g., wider than 1 mm A potential advantage in this configuration is inthat concurrent activation of the PE elements and concurrent fullrotation of the US transducer container 100 forms two adjacentcircumferential lesion rings effecting a dual lesion block.

A potential advantage of the configuration depicted in FIGS. 1G-1J arein that by adding an additional PE element 140 e.g., on the proximal anddistal sides of the cooling channel 120 enables to measure the alignmentof the PE element 140-2 with respect to the tissue.

In cases in which a PE emitting surface is at an angle with respect tothe tissue (i.e., not parallel), the acoustic footprint on the tissuewill be larger (like a shadow of a flashlight aimed at an angle onto asurface). The implication of a larger acoustic footprint is that theenergy per area distributed on the tissue is smaller Therefore, it ismore difficult to ablate the tissue at the same energy level. If theangle of the emitting surface with respect to the tissue target surfaceis known, the required increase in the energy level can be calculated.

Hence, a potential advantage of a configuration having two or moreinclined emitting surfaces is in that a system processor is in that itprovides e.g., a system processor to measure the parallelism, the anglesof the emitting surfaces with respect to the target tissue, compute theUS beam energy required to ablate and adjust accordingly the PE elementemitted US beam. In some embodiments, for example, an angle of theemitting surface 142 with respect to the target tissue surface above 10degrees, 15 degrees or 20 degrees requires an increase of 7%, 14% or 25%respectively.

A potential advantage in having an emitting surface positioned at anangle with respect to a second leveled emitting surface is in that sucha configuration improves the detection of a signal emitted from theangled emitting surface and reflected from the tissue towards leveledemitting surface.

In some embodiments, the angled emitting surface is angled such that afirst axis perpendicular to the angled emitting surface crosses a secondaxis perpendicular to the leveled emitting surface at a distance between5 mm and 25 mm, 7 and 20 mm or 10 mm and 17 mm.

In some embodiments, and as shown in FIGS. 1G, 1H, II, 1J and 1K, PEelement 140-1 is configured to detect an US signal emitted from PEelement 140-2 and reflected off targeted tissue. Optionally andalternatively, PE element 140-2 is configured to detect an US signalemitted from PE element 140-1 and reflected off targeted tissue.

In some embodiments, a first PE element e.g., 140-1 is positioned suchthat it faces an expected US signal emitted from a second PE elemente.g., 140-2 and reflected off targeted tissue.

In the exemplary embodiments depicted in FIG. 1K, US transducercontainer 100 comprises two pair of PE elements 140-1/140-2 and 140-1a/140-2 a placed side-by-side. A potential advantage ion thisconfiguration is in that PE elements 140-1/140-2 and 140-1 a/140-2 a canbe positioned and angled to provide imaging and ablative resultssuitable for any desired specific procedure.

In some embodiments, US transducer container 100 comprises a pluralityof PE elements arranged axially along US transducer container 100. Insome embodiments, two or more consecutive PE elements of the pluralityof PE elements comprise at least two ablative PE elements. In someembodiments, the two or more consecutive PE elements define between thema gap (e.g., 528, FIGS. 5G, 5H, 5I) greater than 1 mm in width. In someembodiments, a first PE element comprises both an ablative and a sensor(imaging) configured to send and receive an US signal during ablation.In some embodiments, the ablative and a sensor (imaging) PE element isconfigured to detect signals returning directly to the PE element alongan ablative US emission line.

In some embodiments, a second PE element acts only as sensor (imaging)that only receives signals between ablation pulses. A potentialadvantage in a second PE element acts only as sensor (imaging) is inthat the treatment area is larger and there is an increased ability todetect returning signals that are deflected away from the directablation line. Additionally, a second PE element acts only as sensor(imaging) can detect signals from a close distance because the PEelement it is at a resting state before the signal arrives andtherefore, the arrived signal is cleaner (has less noise/ringing thatare typically associated with an element that vibrate when it receives asignal).

In some embodiments, different PE elements of US transducer container100 operate at different frequencies. E.g., ablative PE element/soperate in a frequency range greater than 8 mHz, while an imaging PEelement/s operates at a different, lower range and works in pulse-echomode. In this configuration, the ablative PE element ablates tissue andthe imaging PE element transmits and receives its own imaging signalfrom the ablated area (pulse-echo mode). The pulse-echo modeconfiguration stems from the imaging PE element operates on lowerfrequencies and hence cannot detect the higher frequency signal of theablative PE element. A potential advantage in this configuration is inthat lower frequency PE elements allow for deeper signal penetration.Low frequency PE elements cannot be used for ablation purposes becauseof the greater difficulty in forming ablative lesions with low frequencyUS signals.

In some embodiments, PE elements used for imaging comprise an array ofat least four smaller PE elements. A potential advantage in thisconfiguration is in increased image resolution.

In some embodiments, a method for use of a combination of a scanning PEelement and an ablating PE element or a single scanning and ablating PEelement e.g., in ablating one or more ostia of the pulmonary veins andas depicted in FIGS. 1F to 1K, comprises:

Positioning US transducer container 100 at an ostium of a blood vessel;

rotating the transducer about its axis and scanning the vein ostium;

recording one or more returned signal/s from the tissue for creating abaseline image of the vein ostium;

concurrently or consecutively, measuring the vessel wall thickness;

ablating vessel tissue in the vein ostium in consecutive segments byrotating the transducer segmentally until full rotation is completed;

recording the returned signal/s of the ablated segments in real-time andcreating a real-time image based on the one or more returned signals;

comparing the returned signal/s and/or images acquired during-ablationto the acquired baseline return signal/s and/or image created therefrom;

identifying changes in the return signal/s and/or image acquiredduring-ablation that represent changes in the tissue that correspond toablation lesion formation; and

terminating ablation after returned signal/s and/or image changesbetween baseline returned signal/s and/or image and acquired returnedsignal/s and/or image indicate an achieved predetermined level ofablation.

Catheter Ultrasound Transducer Cooling System

In some embodiments, and as shown in FIG. 1 catheter US transducercontainer 100 comprises a cooling system 200 configured to cool PEelement 140 and maintain a container blood-contact surface 116temperature at or below 45 degrees Celsius. In some embodiments, coolingsystem 200 comprises a cooling fluid inlet 152, a cooling fluid outlet154 and a trough-form cooling channel 120 in between. In someembodiments, trough-form cooling channel 120 is defined by a floor 108,bordered by a first and a second side walls 122/124 extending from bothsides of floor 108 and along both lateral sides of emitting surface 142.First and a second side walls 122/124 span between floor 108 and cover130 and sealingly meet edges of container blood-contact surface 116 toform an aperture 118 in container 100.

In some embodiments, cover 130 comprises at least two surfaces: a PEelement 140-facing surface and a blood contact surface 116 facing awayfrom PE element 140. In some embodiments, blood-contact surface 116 isthe outermost surface of cooling channel 120. In some embodiments,blood-contact surface 116 comprises an interface between cooling channel120 and blood surrounding container 100 and catheter 106. In someembodiments, cover 130 forms a barrier that maintains the coolant fluidwithin cooling channel 120 and prevents blood from making contact withPE element 140 and/or cooling system 200. Such contact may lead to bloodclotting.

In some embodiments, and as explained in greater detail elsewhereherein, walls 122/124 are inclined imparting a trapezoid cross-sectionto cooling channel 120 the smaller trapeze base forming floor 108. Insome embodiments, the cross section of the cooling channel 120 hastrapezoid geometry at least over 50% of its length. In some embodiments,the cross section of the cooling channel 120 has trapezoid geometry atleast over 75% of its length.

Any one of PE elements 140/140-1/140-2/140-3 can function as an USablating element and/or an US imaging transducer. For example, in FIG.1G, PE element 140-2 may function as an US transducer whereas PEelements 140-1 and 140-3 may function as US ablation elements.Optionally and alternatively, and as described in detail elsewhereherein, in the embodiments depicted in FIGS. 1A-1G as well asembodiments described elsewhere herein PE element 140 may function as anUS ablation element and/or an US transducer element. In someembodiments, and as discussed elsewhere herein, PE element 140 isdisposed inside cooling channel 120 and is mounted on one or more posts102. In some embodiments, dimensions of cooling channel 120 are equal toor larger dimensions of PE element 140. E.g., In some embodiments, alength of cooling channel 120 is at least the same as the length of PEelement 140. In some embodiments, it is shorter than PE element 140.

In some embodiments, and as shown in FIGS. 2A, 2B and 2C, walls 122/124are inclined sloping radially inwards at an angle (g) between 1 and 45degrees from the perpendicular 202 to floor 108. In some embodiments,angle (g) is between 10 and 30 degrees or 15 and 25 degrees from theperpendicular to floor 108.

A potential advantage in a trapezoid cross-section of cooling channel120 is in that inclined walls 122/124 form an unobstructed pathway foran US beam 204 emitted from emitting surface 142 of PE element 140. Apotential advantage in a trapezoid cross-section of cooling channel 120is in that inclined walls 122/124 provide easy access to floor 108 formounting of PE element 140 during manufacturing.

Catheter US Transducer Container

FIG. 2C, which is a thermal image of an US beam distribution pattern ofan acoustic beam emitted from an US PE element 140 in perpendicular tothe emitting surface 142 via cooling channel 120, depicts the pressure(Pmax) of the emitted beam along an X-axis (i.e., along a transversecross-section of PE emitting surface 142) as a function of a height (h)(FIG. 2A) between emitting surface 142 and cooling channel 120 cover130. As depicted in the exemplary embodiment shown in FIG. 2C, a marginclear of any US acoustic pressure is represented by a deep blue color148 on both sides of an emitted beam 150 showing the full beam 150 spanto be emitted with no interference. As shown in FIG. 2C, the acousticbeam emitted from an US PE element 140 is unobstructed as it travelsthrough and out of cooling channel 120.

Reference is now made to FIG. 3A, which is a perspective view simplifiedillustration of catheter US transducer container 100 and US transducercontainer 100 cooling system 200 and to FIGS. 3B and 3C, which aregraphs demonstrating heat distribution within cooling system 200 inaccordance with some embodiments of the invention. In some embodiments,cooling system 200 is configured to cool PE element 140 as well as forma closed-circuit system, heat transfer buffer zone 160 between PEelement 140 and blood-contact surface 116 configured to maintain acontainer 100 blood-contact surface 116 temperature at or below 45degrees Celsius to decrease the risk of blood clotting and emboligeneration. As shown in FIG. 3C, the temperature of the cooling fluid inbuffer zone 160 drops as the distance of the fluid from PE element 140increases as indicated by an arrow 350.

In some embodiments, buffer zone 160 is formed inside cooling channel120 between emitting surface 142 and cover 130 by generating atemperature gradient in cooling fluid within cooling channel 120 asexplained in greater detail elsewhere herein. In some embodiments, thecooling gradient is achieved by a laminar-uniform flow of the coolingfluid at least over emitting surface 142 of PE element 140 and formed bycooling channel 120 generally flat floor, flat emitting surface 142 ofPE element 140 and flat cover 130, supplied by an acoustically matcheddedicated cooling fluid inlet 152 at one end of channel 120 andevacuated by a dedicated cooling fluid outlet 154 at the other, oppositeend of channel 120. In some embodiments, the rate of flow of the coolantfluid is adjusted to the viscosity of the fluid and fluid velocity ismaintained below a threshold at which it becomes turbulent.

In some embodiments, a temperature sensor 166 at the blood-contactsurface 116-blood interface (or temperature within the flow channel)controls the rate of flow rate needed to maintain a temperature of theblood barrier below a target temperature needed to prevent bloodcoagulation.

In some embodiments, the system is configured to vary the cooling fluidflow rate and change the effective temperature at the blood-contactsurface 116-blood interface. For example, in some embodiments, the flowrate is increased to cool down the blood-contact surface 116-bloodinterface.

In some embodiments, the system is configured to vary the temperature ofor at the fluid inlet 152 based on temperature readings of temperaturesensor 166 at the blood-contact surface 116-blood interface (ortemperature within the flow channel) and maintain an unchanged flowvelocity.

Optionally, the system is configured to vary the temperature of or atthe fluid inlet 152 and vary the flow of the cooling fluid based ontemperature readings of temperature sensor 166 at the blood-contactsurface 116-blood interface (or temperature within the flow channel).

The flow rate and variation in flow rate depends on at least one of thearea cross-section of cooling channel 120, the area of blood-contactsurface 116-blood interface, temperature of the cooling fluid andvariation in vessel blood temperature. To cool down blood-contactsurface 116-blood interface and given cooling channel 120 channeldimensions, the velocity of the cooling fluid over the ablating elementin some embodiments, is between 5 cm/sec-60 cm/sec. In some embodiments,the velocity of flow is between 15 cm/sec-50 cm/sec. In someembodiments, the velocity of flow is between 20 cm/sec-30 cm/sec. is 25cm/sec.

A potential advantage in this system configuration is in that the systemcooling channel has a small cross-section e.g., smaller than a diameterof catheter 106 (between 0.01-0.5 of the diameter of catheter 106)configured to generate a velocity of flow sufficiently high to achieveefficient cooling, below 45 degrees Celsius at the blood-contact surface116-blood interface.

The structure of cooling system 200 provides laminar-uniform flow overemitting surface 142 of PE element 140 in a direction indicated by arrow180. In some embodiments, the flow rate of the cooling fluid is between5 ml/sec and 400 ml/sec. In some embodiments, the flow rate of thecooling fluid is between 50 ml/sec and 300 ml/sec. In some embodiments,the flow rate of the cooling fluid is between 75 ml/sec and 200 ml/sec.

In some embodiments, container 100 comprises one or more temperaturesensor 166 at the blood-contact surface 116 of container 100 cover 130and the flow rate is adjusted in accordance with a temperature measuredat blood contact surface 116. For example, when the measured temperatureat blood-contact surface 116 exceeds 45 degrees Celsius, blood flow frominlet 152 is increased accordingly.

In some embodiments, container 100 comprises one or more temperaturesensors 168 in gap 104 between PE element 140 and floor 108 of coolingchannel 120 or adjacent to PE element 140. In some embodiments, the flowrate is adjusted in accordance with a temperature measured in gap 104 tomonitor and control PE element 140 temperature during operation.

FIGS. 3B and 3C are a graph (FIG. 3B) and heat distribution map (FIG.3C) depicting a temperature gradient in cooling channel 120 with respectto the level of the fluid layer measured by distance (L) from PE element140 emitting surface 142. As shown in FIG. 3B, the greater the distance(L) between a fluid layer and PE element 140 emitting surface 142, thelower the temperature, dropping as shown in FIG. 3B from approximately120 degrees Celsius at emitting surface 142 to approximately 45 degreesat blood-contact surface 116 which is at the greatest distance @ma) fromUS beam emitting surface 142.

It is also noted in FIG. 3B, that the temperature continues to drop tobelow 45 degrees Celsius beyond blood-contact surface 116 in blood flowlayers adjacent to blood contact surface 116. Optionally, the coolantfluid is cooled to below 37 deg C. at blood contact surface 116, inwhich case the blood temperature which is normally at 37 deg C. will notdrop in the layers beyond the blood contact surface 116.

A potential advantage in the cross-section profile of cooling system 200is in that the laminar flow of cooling fluid in cooling channel 120generates an effective and uniform blood-contact surface 116-bloodinterface and provides for a rapidly formed homogeneous temperatureprofile of the blood-contact surface 116-blood interface with no heatzones.

A potential advantage in the cross-section profile of cooling system 200is in that the laminar flow of cooling fluid in cooling channel 120 isconfigured to and effective in removal of gas (e.g., air) bubbles formedin cooling channel 120, e.g., bubbles adhered to PE element 140-facingsurface of cover 130.

Component of the PE Element Cooling System

In some embodiments, a processor (not shown) is used to calculate andoptimize signal transmission and sensing data (e.g., temperature,distance from organ wall, wall thickness, power application time, changein amplitude and phase of returned signal) to optimize power output(e.g., for ablation), transducer reliability and lesion size. In someembodiments, container 100 comprises a PE element temperature sensor 166that communicates with the processor. The processor is configured toincrease or decrease power input based on the data received from thepiezoelectric temperature sensor.

In some embodiments, the system processor is configured to adjust thelevel of energy emitted from the PE element based on one or more ofdistance measured from the emitting surface of the PE element to saidtissue wall, tissue thickness, duration of energy delivery, change inamplitude and/or phase of ultrasound signal returning from the tissueand reduction of recorded electrical potential signals.

In some embodiments, adjustment of the energy level is based onimpedance measurement between one or more tissue contact electrodes 725on positioner 702 and on one or more electrical electrodes, not incontact with the tissue located on the catheter 106 shaft or UStransducer container 100.

In some embodiment, a processor (not shown) is configured to calculatespeed of transducer rotation via a motor (not shown) positioned in thecatheter handle (not shown) to optimize power output for optimal lesioncreation based on sensing data (e.g., distance from organ wall, wallthickness, power application time, change in amplitude and phase ofreturned signal). Alternatively, and optionally, the processor isconfigured to calculate transducer rotation based on a gyroscopeembedded within a handle (not shown) of catheter 106. A potentialadvantage of a gyroscope is in its ability to show absolute angles ofthe catheter/ultrasound transceiver that allows physicians to return toa registered angular position during the procedure.

In some embodiments, the processor receives data from both blood-contactsurface temperature sensor 164 and PE element temperature sensor 166 andbased on the current cooling fluid flow rate extrapolates a temperaturegradient between emitting surface 142 and blood contact surface 116 andincreases or decreases power input to PE element 140 accordingly.

In some embodiments, US transmission duty cycle is maintained greaterthan 60% to cool down US transducer PE element 140 without effecting therate of energy transfer to tissue required to elevate tissue temperatureabove 50 deg needed to form tissue lesion.

Other means used to maintain a relatively cool temperature of PE element140 comprise using a pulse repetition frequency to lower transducertemperature, increase flow rate, decrease coolant fluid temperature,lower duty cycle, and regulate voltage based on distance from tissuewall to regulate time needed for successful ablation.

Bubble Control

Bubbles commonly formed by cavitation effect or air trapped in the inletand/or outlet tubes pose a common interference issue in US transmissionby forming one or more non-acoustically matched surfaces that reflectportions of the emitted US beam in unexpected directions. This isespecially found in configurations that involve cooling systems thatcirculate a coolant within a balloon enveloping the US transducer.Bubbles are often trapped and adhered to a curved wall of the balloon,where circulation is insufficient to dislodge the bubbles and whensuccessful, the coolant fluid flow in the vicinity of the bubbles isturbulent and just arbitrarily moves the bubbles from one location toanother.

As shown in the exemplary embodiment depicted in FIGS. 4A and 4B, whichare side cross-section view and transverse cross section view takenalong line B-B, simplified illustrations of the effect of laminarcooling fluid flow on bubbles in accordance with some embodiments of theinvention, a bubble 402, formed within cooling channel 120 is maintainedaway from emitting surface 142 and cooling channel cover 130 by laminarflow 450 and is carried towards cooling fluid outlet 154 positioned incooling fluid diverting chamber 156 at tip 158 of the container 100where it is suctioned out of the catheter 106 by vacuum within coolingfluid outlet 154 or by means of pressure head forcing the fluid towardsthe cooling fluid outlet 154.

In some embodiments, the confined channel cross-section adds to theeffect of the laminar cooling fluid flow by limiting the wall surface towhich a bubble may adhere as well as increase the fluid pressure appliedto a bubble that appears. As shown in FIGS. 4A and 4B, bubbles thatappear are urged into cooling fluid cooling fluid diverting chamber 156at tip 158 of container 100 and by a down flow towards fluid outlet 154.An additional advantage in the configuration of the laminar flow incooling channel 120 as well as the flow directionality is in that itremoved risk of ultrasound transmission interference due to air bubblesand negates the need for use of degassed fluid or in-line bubbledetection sensors and/or traps.

In some embodiments, an area of a cross-section of cooling channel 120constitutes between 0.01 and 0.5 of an area of a cross-section of thecatheter 106 at the same location. In some embodiments, an area of across-section of cooling channel 120 constitutes between 0.1 and 0.4 ofan area of a cross-section of the catheter 106 at the same location. Insome embodiments, and at least one ultrasound transducer one or more PEelements 140 are disposed within and on a floor 108 of the channel 120.

A potential advantage of laminar cooling fluid flow within the coolingchannel is in that heat transfer by the coolant is predictable andcontrolled by manually or automatically adjusting the flow rate and theflow parameters can be predefined (and simulated) with respect to therequired ultrasound parameters.

A potential advantage of laminar cooling fluid flow within the coolingchannel is in a uniform temp distribution throughout US transducercontainer 100 and faster flow adjustment expressed by faster control ofblood contact surface temperature adjustment. Uniform temperatureeliminates hot zones from forming at the blood contact surface 116.

In some embodiments, the maximal volume of the coolant within the UStransducer container 100 is lower than 14,200 mmA3. In some embodiments,the maximal volume of the coolant within the US transducer container 100is lower than 25 lmmA3 In some embodiments, the volume of the coolantwithin the US transducer container 100 at any given time is between 1mmA3 to 40 mmA3.

According to some embodiments, the US transducer is configured to beinserted into an organ (e.g., a blood vessel) via a catheter. In someembodiments, the external diameter of the US transducer container 100 issmaller than the diameter of a catheter 106 configured to insert the UStransducer into an organ. In some embodiments, as shown in section A-Aof FIG. 1, the cross section of container 100 is reduced at the level ofcooling channel 120 cover 130. In some embodiments the cover 130 is madeof a high heat absorbing material. In some embodiments the cover 130 ismade of a low acoustic attenuation material. In some embodiments, cover130 thickness is below 1 mm, below 0.5 mm or below 0.3 mm.

In some embodiments, the distance between the external surface of the UStransducer and the tissue is monitored, such as the power supplied tothe transducer is increased or decreased based on the monitoreddistance. In some embodiments, the distance between the transducer andthe tissue is monitored, such as the power supplied to the transducer isincreased or decreased based on the monitored distance. In someembodiments, the distance between the transducer and the tissue ismonitored, such as the power supplied to the transducer is manually orautomatically stopped if the monitored distance is below a predeterminedsafe distance. In some embodiments, a safe distance is defined by adistance above 1 mm. In some embodiments, a safe distance is defined bya distance above 2 mm. In some embodiments, a safe distance is definedby a distance above 5 mm. In some embodiments, the treatment durationand/or power is regulated based on analysis of the signals returned fromtissue, detection of lesion formation in the tissue and completion oflesion created. In some embodiments, the treatment duration and/or poweris regulated based on one or more of the following measurements andcalculations: distance from tissue, tissue thickness, transducer dutycycle, transducer pulse repetition frequency, voltage, amplitude ofreturn signal from targeted area, rate of change of amplitude ofreturned signal, phase change of signal return from targeted area,reduction of recorded electrical potential signals e.g., signalsrecorded from the pulmonary veins and/or impedance measurement between atissue contact electrode attached to the positioner 702 and anon-contact electrode attached to the catheter shaft or US housing. Insome embodiments the US transducer comprises one or more computing unitswhich receive sensors data as an input and outputs transducer operationparameters.

Transducer Design and Manufacture

Reference is now made to FIGS. 5A, 5B, 5C, 5D, 5E, 5F, SC, 5H and 5I,which are perspective view and cross section view simplifiedillustration of method of manufacturing a container transducer inaccordance with some embodiments of the invention. As shown in FIG. 5A,a container 100 comprises a housing 502 comprises a trough-shaped fluidchannel 120 having one or more supports 504 for PE element 140.

In some embodiments, PE element 140 support 504 are made ofnon-electrically conductive high temperature capacity material so thatheat produced by PE element 140, positioned on supports 504, duringoperation is absorbed by the proximal and distal PE element 140 supports504. In some embodiments, US PE element 140 comprises a middle partitionmade of a non-electrically conductive material that insulates betweentransducer electrodes connected at the distal end and the proximal endof the transducer ceramic.

In some embodiments of the current invention, the catheter US transducercomprises an internal heat conducting lumen, connected at its distal endto one or more of: US transducer surface, transducer support, therebytransferring heat out of the US transducer.

In some embodiments, housing 502 comprises an electrical conduit 506 fora PE element 140 temperature sensor 166 and a conduit 508 for electricalwiring as will be explained in greater detail herein. In the exemplaryembodiment shown in FIG. 5B, an electrical wire 510 has been insertedinto housing 502 and laid out prior to being connected to PE element140.

FIGS. 5C and 5D, which are side cross-section view simplifiedillustrations of wiring options for PE element 140 in accordance withsome embodiments of the invention. As shown in FIG. 5C, wiring of PEelement 140 comprises two or more electrodes, a first electrode 512along PE element 140 emitting surface 142 and a second electrode 514along an opposite surface of PE element 140 facing floor 108 of coolingchannel 120. Electrodes 512 and 514 are isolated from each other.

Alternatively, and optionally, and as shown in FIG. 5D, wiring of PEelement 140 comprises two or more electrodes, a first electrode 516along at least a portion of PE element 140 emitting surface 142 andaround one end of PE element 140 and a second electrode 518 along atleast a portion of an opposite surface of PE element 140 facing floor108 of cooling channel 120 and around an opposite tip 158-facing end ofPE element 140. Electrodes 516 and 518 are isolated from each other byone or more gaps 530/536 on the emitting surface 142 as well as on theopposite surface facing floor 108 respectively.

In some embodiments, one or more gaps 530/536 are bridged by aninsulating adhesive. In FIG. 5D, the gap 536 on the emitting surface 142of PE element 140 is bridged by an insulating adhesive 532.

A potential advantage of the wiring configurations is in that thisconfiguration nullifies the need to isolate PE element 140 withnon-conductive material, e.g., Parylene. This is achieved by positioningat least two contacts on generally opposite sides of the PE element 140,while maintaining and the PE element 140 circumferentially insulatedwith insulating material e.g., an electrical insulating adhesive. Thisprevents any potential electrical short between the two sides of the PEelement.

A potential advantage in the use of a non-conductive material, e.g.,Parylene to isolate PE element 140 is in that it simplifies themanufacturing process and is less expensive than other commonly usedtechniques. Reference is now made to FIG. 5E, which is a cross sectionof US transducer container 100 as taken along section C-C shown in FIG.5B and shows wire 510 exiting conduit 508 and placed in contact with tip158-facing end of PE element 140. In some embodiments, container cover130 comprises one or more micro outlet ports 195 that allow fluidoutflow from cooling channel 120 into the surrounding blood stream. Apotential advantage of micro outlet ports is in that fluid exiting themicro ports washes off any blood residue/charring that may form duringthe ablation process.

FIG. 5F, is a cross section view simplified illustration of housing 502electrical and fluid passages to catheter 106 as viewed from a directionindicated in FIG. 5B by, an arrow 550. As shown in the exemplaryembodiments depicted in FIG. 5F, housing 502 comprises conduits forcooling fluid inlet 152 tube and cooling fluid outlet 154 tube and atransducer housing support tube 520 having a lumen 126. In someembodiments, transducer housing support tube 520 and lumen 126 are sizedto accommodate a guide wire 524 conducting tube 526. In someembodiments, housing 502 comprises one or more conduits 508 for one ormore ablation PE elements 140 coaxial cables and one or more conduits522 for one or more inclined PE elements 140 coaxial cables.

FIGS. 5G, 5H and 5I depict the manufacturing process of US transducercontainer 100 following the electrical wiring of US transducer container100. FIG. 5G shows the stage of manufacturing following the previousstages described herein and comprises connecting electrical conductors506/510 to the corresponding ends of PE element 140 in accordance withthe connection options described elsewhere herein. The step ofconnection of electrical wires is followed in some embodiments, and asshown in FIG. 5H by attaching fluid inlet 152 and fluid outlet 154 to acooling fluid diverting chamber 156 within tip 158 of the container asshown in FIG. 51. The perimeter 534 of PE element 140 is sealed to walls122/124 of cooling channel 120 and posts 102 with a flexible isolatingand fluid proofing adhesive e.g., Epoxy adhesive, UV adhesive or Siliconadhesive (e.g., Dymax 204-CTH, Dymax 1191, Epo-Tek 301 or Epo-Tek 353ND)thus Insulating cover 130 is comprises a polymer (e.g., Polyester orPebax®) is then placed over housing 502 as in shrunken (e.g., byexposure to heat) to tightly seal housing 502.

The process is finalized by attaching cooling channel cover 130 overhousing 502 and non-spherical part of the container tip 158.

Reference is now made to FIG. 6, which is a flow chart of a method ofmanufacture and assembly of a US transducer container 100 in accordancewith some embodiments of the invention. As shown in FIG. 6, the methodcomprises at 602 molding a housing 502 comprising one or more fluidconduits, one or more electrical conduits 506/510, one or moretemperature sensor 166 conduits, one or more main catheter lumen 126,and one or more trough-shaped cooling channels 120.

In some embodiments, cooling channel 120 comprises a trough-form coolingchannel 120 defined by a floor 108 including one or more posts 102 andbordered by a first and a second side walls 122/124 extending from bothsides of floor 108 and along both lateral sides of emitting surface 142and meet edges of container blood-contact surface 116 to form anaperture 118 in container blood-contact surface 116.

At 604, electrical conduit 506/510 of PE element 140 is laid within therespective conduits, in communication with and leading through catheter106 to a respective source/s of power and/or communication (not shown).

At 606, PE element 140 is mounted on one or more posts 102 and connectedto electrical conductors 506/510 as explained in detail elsewhereherein. In some embodiments, and optionally, the method comprisescoating PE element 140 with a dielectric layer. In some embodiments, andoptionally, the method comprises applying a dielectric material betweenends of electrical conductors 506/510 connected to PE element 140. At608, sealing the perimeter of PE element 140 to walls 122/124 of coolingchannel 120 with a flexible isolating and fluid proofing adhesive and at610 attaching a cooling fluid diverting chamber 156 and tip 158 of thecontainer. In some embodiments, steps 606 and 608 are combined to asingle step. The process is completed by placing over housing 502 aninsulating covers a portion of which, in some embodiments, comprisescover 130, shrinking the cover (e.g., by exposure to heat) and tightlysealing housing 502 and cooling channel 120.

Positioner

Reference is now made to FIGS. 7A, 7B, 7C and 7D which are plan view andperspective view simplified illustrations of a positioner 702 for acatheter 106 carrying a US transducer container 100 as disclosed herein.In some embodiments, catheter 106 comprises an expandable positioner 702enveloping at least a portion of US transducer container 100. In someembodiments, positioner 702 is mounted on a catheter inserted throughcatheter 106. In some embodiments, positioner 702 is an integral part ofcatheter 106. In some embodiments, and as shown in FIGS. 7A, 7B and 7C,positioner 702 envelops US transducer container 100. In someembodiments, positioner 702 comprises one or more openings 704, thediameter of which is greater than the diameter of the US beam emittedthrough the opening 704 so that positioner 702 does not interfere withpropagation of the beam. In some embodiments, positioner 702 is made ofa shape memory resilient biocompatible material, e.g., Nitinol. In someembodiments, positioner 702 is a non-occluding positioner configured toallow blood flow therethrough.

In some embodiments, positioner 702 comprises a cage-like geometry. Insome embodiments, positioner 702 comprises a basket-like geometry. Insome embodiments, positioner 702 comprises a cylinder-like geometry. Insome embodiments, dimensions of a cylindrical positioner 702 are between10 mm-30 mm in diameter and 7 mm-60 mm in length. In some embodiments,dimensions of a cylindrical positioner 702 are between 15 mm-25 mm indiameter and 1.0 mm-50 mm in length. In some embodiments, dimensions ofa cylindrical positioner 702 are between 17 mm-20 mm in diameter and 8mm-40 mm in length.

In some embodiments, the geometry of positioner 702 and location ofopenings 704 in positioner 702 is non-uniform e.g., the openings 704 arelocated at the distal portion of positioner 702 such that one portion ofpositioner 702 e.g., a proximal portion, provides mechanical support andanother portion e.g., a distal portion provides less mechanical supportand more exposure (more openings 704) to allow for more effectiveacoustic ablation.

In some embodiments, positioner 702 comprises a detachable from thecatheter. In some embodiments, positioner 702 comprises a detachableplug, e.g., configured to plug cavities in the left atrium such as LeftAtrial Appendage following an ablation treatment.

In some embodiments, positioner 702 comprises contact and/or non-contactelectrodes 725 and is configured to record electrical activity before,during and/or after ablation to monitor procedure effectiveness.

In some embodiments, and as depicted in FIGS. 7A and 7B, positioner 702has an ovoid geometry. In some embodiments, and as depicted in FIG. 7C,positioner 702 comprises a positioner 702 has a diamond geometry or anyother suitable geometry.

FIG. 7D, which is a perspective view simplified illustration ofimplementation of US transducer container 100 and positioner 702 inaccordance with some embodiments of the Invention. As shown in theexemplary embodiment depicted in FIG. 7D, US transducer container isimplemented in contactless ablation of ostia of the pulmonary veins inthe left atrium of the heart. In this procedure, a US transducercontainer 100 configuration can be employed using an ablative inclinedPE element 140 and an imaging PE element 140-1 as described elsewhereherein. Positioner 702 is expanded inside the left atrium lumen anddirected towards one of the four main pulmonary veins ostia. Once thepositioner 702 is positioned in contact with walls of the pulmonary veinostium, US transducer container 100 is automatically positioned,generally centered in the ostium to allow safe ablation of the ostiummargins. In some embodiments, US transducer container is configured tobe rotatable within positioner 702 as indicated by arrow 750 and ablatea ring encompassing the margin of the pulmonary vein ostium. In someembodiments, US transducer container is configured to axially translatein a bidirectional manner within positioner 702 to better position UStransducer container 100 within, for example, a pulmonary vein ostium. Apotential advantage of this feature is in that linear movement of UStransducer container 100 provides for linear ablation (e.g., in parallelto the axis of translation of US transducer container 100) of the tissuein selected anatomies.

In some cases, such as, for example atrial fibrillation treatment, thepulmonary vein is ablated to stop the ectopic cardiac action potentialtrigger. In such treatments, a balloon-type positioner or coolingballoon, commonly used in such procedures, is inflated to a point atwhich the balloon surface is urged against a vessel wall thusstabilizing the ablating element. However, when a cooling balloon isused to cool and center a transducer a blood vessel (e.g., within thepulmonary vein) and the balloon wall contacts the pulmonary vein tissue,blood might be trapped and pooled between the balloon and the tissue.The pooled blood may potentially coagulate due to heat generated by thetissue during ablation. Deflation of the balloon at the end of theprocedure may release the newly formed blood clot which may become astroke risk.

A potential advantage of a non-occluding positioner is in that it isconfigured to allow blood to flow therethrough significantly reducing oraltogether preventing blood pooling and/or clotting and formation ofblood embolism.

Jet Effect

Reference is now made to FIG. 8, which is a cross-section viewsimplified illustration of implementation of a catheter US transducercontainer in accordance with some embodiments of the invention. In someembodiments. US transducer container 100 is sized and fitted to bepositioned along or within a catheter 106. In some embodiments, UStransducer container 100 comprises a collimating acoustic lens 802.

To the surprise of the authors of this disclosure it was observed thatin some embodiments, collimated beam energy generated from a suitablydesigned US transducer PE element 140 generates a jet effect 850 insurrounding blood stream having the same temperature as that of thesurrounding blood stream. In some embodiments, the collimated beamenergy is above 50 W/cmA2. In some embodiments, the collimated beamenergy is above 70 W/cmA2. In some embodiments, the collimated beamenergy is above 90 W/cmA2.

A potential advantage in such a jet effect 850 is in that a jet aimed ata treatment area cools the tissue wall 808 at the point of penetrationof the ultrasound beam into the tissue and prevents tissue charring.

In some embodiments, catheter 106 comprises one or more therapeuticagent delivery nozzles 804 configured to deliver a therapeutic agent 806into the blood stream, e.g., up-stream to US transducer container 100 sothat therapeutic agent 806 flows into emitted US beam 204 and is drivenby the jet effect 850 towards the tissue wall 808.

It has also come to be known to the authors of this disclosure that toosmall a cross-section dimension (e.g., area) does not generate a jeteffect or that the generated jet would not be effective in driving atherapeutic agent 806 towards a small tissue wall 808 area.Alternatively, a too large cross-section dimension (e.g., area) wouldrequire a high level of driving energy, beyond the maximal energyrequirement for the device.

It was found that in some embodiments, an optimal cross-sectiondimension (e.g., area) for generating a jet effect sufficientlyeffective in driving a therapeutic agent 806 towards a small tissue wall808 area should be sufficiently small (e.g., high energy percross-section area) and is in the range between 8 mmA2 to 30 mmA2. Insome embodiments, an optimal cross-section dimension (e.g., area) is inthe range between 12 mmA2 to 20 mmA2. In some embodiments, an optimalcross-section dimension (e.g., area) is in the range between 14 mmA2 to16 mmA2.

FIG. 9 is a transverse cross-section simplified illustration of amultidirectional US transducer container, according to some embodimentsof the invention. In some embodiments, a multidirectional USscanner/ablating transducer container 900 includes a plurality of PEElements 140, arranged circumferentially about a longitudinal axis ofcontainer 900. In some embodiments, each PE element is arranged within acooling channel 120 and includes coolant fluid inlet and outlet andelectrical conductors as explained elsewhere herein.

In some circumstances, in addition to catheter ablation for atrialfibrillation treatment as explained in detail elsewhere herein, there isa need to form lesions (e.g., lesion lines) in non-pulmonary vein ostiumlocations e.g., between the left inferior pulmonary vein to the mitralvalve, between the left pulmonary veins to the right pulmonary veinsalong the posterior wall (LA roof line & LA floor lines) and/or inselected areas in the left atrium where ectopic cardiac action potentialtriggers are identified.

Reference is now made to FIGS. 10A and 10B, which are perspective viewsimplified illustrations of a catheter US transducer container includingone or more RF electrode tips forming an US transducer/RF combinationcatheter container 1000. In some embodiments, and as shown in FIGS. 10Aand 10B, the US transducer/RF container 1000 tip 158 comprises ametallic material such as, for example, iridium/platinum, platinum,copper or gold. In some embodiments, the US transducer/RF combinationcatheter container 1000 tip 158 comprises an RF electrode 1002electrically connected via one or more electrical conductors, similar toelectrical conductors 506/510, to an RF power source (not shown). Insome embodiments, container tip 158 comprises one or more irrigationports 1004 configured to eject cooling fluid (e.g., saline) to cool RFtreated lesions and/or tissue surrounding the treated lesions. In someembodiments, US transducer/RF combination catheter container 1000 RFelectrode 1002 is configured to come in contact with tissue and formlesions at the tissue.

A potential advantage in an US transducer/RF combination cathetercontainer is in the ability of the device to treat not only pulmonaryveins (PV) ostia but also to form additional lesion lines that might berequired or desired after completion of pulmonary vein electricalisolation.

A potential advantage in a US transducer/RF combination ca container isin that such a combination container is configured to effect:

a. Radially outward directed US ablation, resulting in circumferentialpulmonary vein (PV) electrical isolation; andb. Point-by-point RF ablation targeting non-PV ectopic cardiac actionpotential triggers.

A potential advantage in a US transducer/RF combination cathetercontainer is in that such a combination container is configured forcombining different types of energy (e.g., US and RF energies) toincrease treatment diversity of the device:

a. Radially outward directed US ablation, resulting in circumferentialpulmonary vein (PV) electrical isolation; and

b. Forward directed contact RF ablation for specific non-PV ectopiccardiac action potential triggers.

In some embodiments, and as shown in FIG. 10B, US transducer/RFcombination catheter container comprises a positioner 702. In someembodiments, positioner 702 is detachable. A potential advantage in thisconfiguration is in that positioner 702 is detachable and configured toplug a cavity e.g., the left atrial appendage.

In some embodiments, positioner 702 is collapsible. In some embodiments,positioner 702 in the collapsed configuration is configured to be drawninto catheter 106. A potential advantage in this configuration is inthat a tissue location can be treated initially with an US transducer,being maintained in place by positioner 702 as explained in detailelsewhere herein, followed by removal of positioner 702 e.g., bycollapse and retrieval into catheter 106, followed by contact RFtreatment employing container tip 158 RF electrode 1002.

Throughout this application, various embodiments of this invention maybe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numberswithin that range, for example, 1, 2, 3, 4, 5, and 6. This appliesregardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

In the description and claims of the application, each of the words“comprise” “include” and “have”, and forms thereof, are not necessarilylimited to members in a list with which the words may be associated. Inaddition, where there are inconsistencies between this application andany document incorporated by reference, it is hereby intended that thepresent application controls.

The descriptions of the various embodiments of the invention have beenpresented for purposes of illustration but are not intended to beexhaustive or limited to the embodiments disclosed. Many modificationsand variations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

1. A method for ablating an ostium of a blood vessel of a subject thatextends from a chamber of a heart of the subject, the method comprising:positioning an ultrasound transducer at the blood vessel ostium;rotating the transducer about its axis and scanning tissue of the bloodvessel ostium; recording one or more baseline returned signals from thetissue and creating a baseline image of the blood vessel ostium based onat least one of the returned signals; ablating tissue of the bloodvessel ostium in consecutive segments by rotating the transducersegmentally until full rotation is completed; recording the returnedsignals of the ablated segments in real-time with respect to theablation of the ablated segments, and creating a real-time image basedon the one or more returned signals; comparing the real-time returnedsignals and/or the real-time image to the baseline returned signalsand/or image; identifying changes in the real-time returned signalsand/or real-time image with respect to the baseline returned signalsand/or baseline image that represent changes in the tissue thatcorrespond to ablation lesion formation; and terminating ablation afterthe identified changes indicate an achieved predetermined level ofablation lesion formation.
 2. The method according to claim 1, whereinthe ultrasound transducer includes at least one scanning ultrasoundpiezoelectric element and at least one ablating ultrasound piezoelectricelement, and wherein scanning the tissue comprises scanning the tissueusing the at least one scanning ultrasound piezoelectric element, andablating the tissue comprises ablating the tissue using the at least oneablating ultrasound piezoelectric element.
 3. The method according toclaim 1, wherein the ultrasound transducer includes at least twoablating ultrasound piezoelectric elements, and wherein ablating thetissue comprises ablating the tissue using the at least two ablatingultrasound piezoelectric elements.
 4. The method according to claim 1,wherein ablating tissue of the blood vessel ostium comprises creatingtwo circumferential ring-lesions.
 5. The method according to claim 1,wherein the blood vessel includes a pulmonary vein, and the chamber ofthe heart includes a left atrium and wherein the method is for use withthe pulmonary vein that extends from the left atrium.
 6. A device foruse with a blood vessel of a subject that extends from a chamber of aheart of the subject, the device comprising: a catheter ultrasoundtransducer comprising one or more piezoelectric elements, and anexpandable positioner configured to envelope at least a portion of thecatheter ultrasound transducer and to position the catheter ultrasoundtransducer in the blood vessel by contacting a wall of the blood vessel,the expandable positioner being configured to allow the catheterultrasound transducer to rotate and axially translate back and forthwithin the expandable positioner.
 7. The device according to claim 6,wherein the one or more piezoelectric elements comprise at least oneablative piezoelectric element configured to ablate tissue of an ostiumof the blood vessel by applying ultrasound energy to tissue of theostium.
 8. The device according to claim 6, further comprising one ormore electrodes located on the expandable positioner and configured tocontact tissue of the blood vessel.
 9. The device according to claim 6,wherein the expandable positioner is in a form of one or more of: abasket, a coil, and an umbrella.
 10. The device according to claim 6,wherein, the expandable positioner comprises at least one opening. 11.The device according to claim 6, wherein the expandable positioner isnon-occluding.
 12. The device according to claim 6, wherein the bloodvessel includes a pulmonary vein, and the chamber of the heart includesa left atrium and wherein the device is for use with the pulmonary veinthat extends from the left atrium.
 13. The device according to claim 6,wherein the one or more piezoelectric elements comprise at least oneimaging piezoelectric element configured to image tissue of an ostium ofthe blood vessel.
 14. The device according to claim 13, wherein theexpandable positioner comp nitinol.
 15. A method, comprising: advancinginto an atrium of a heart of a subject: a catheter ultrasound transducerincluding one or more piezoelectric elements of which at least onepiezoelectric element is an ablative piezoelectric element and at leastone piezoelectric elements is an imaging piezoelectric element, and anexpandable positioner enveloping at least a portion of the catheterultrasound transducer and being configured to allow the catheterultrasound transducer to rotate and axially translate back and forthwithin the expandable positioner; and activating the catheter ultrasoundtransducer to image tissue at a pulmonary vein ostium of the subject byusing the imaging piezoelectric element.
 16. The method according toclaim 15, further comprising activating the catheter ultrasoundtransducer to ablate tissue at the pulmonary vein ostium of the subjectby using the ablative piezoelectric element.
 17. A device for use with ablood vessel of a subject that extends from a chamber of a heart of thesubject, the device comprising: a catheter ultrasound transducercomprising one or more piezoelectric elements mounted at a distal end ofthe catheter ultrasound transducer, the one or more piezoelectricelements configured to ablate tissue of an ostium of the blood vessel byapplying ultrasound energy to tissue of the ostium; a gyroscopeconfigured to detect absolute angles of the catheter ultrasoundtransducer.
 18. The device according to claim 17, further comprising anexpandable positioner configured to envelope at least a portion of thecatheter ultrasound transducer and to position the catheter ultrasoundtransducer in the blood vessel by contacting a wall of the blood vessel.19. The device according to claim 17, wherein the blood vessel includesa pulmonary vein, and the chamber of the heart includes a left atriumand wherein the device is for use with the pulmonary vein that extendsfrom the left atrium.
 20. The device according to claim 17, wherein thegyroscope is embedded in the catheter ultrasound transducer.
 21. Thedevice according to claim 20, wherein the gyroscope is embedded within ahandle of the catheter ultrasound transducer.